1. Field of the Invention
The present invention relates to a positioning device and method, and, more suitably, is applicable to a mounter for carrying semiconductor devices onto a substrate.
2. Description of the Related Art
In the mounter of this sort, a motion pattern of a head is determined using a targeted locus calculated on the basis of a so-called trapezoidal speed command, in controlling the positioning by moving the head for adsorbing a semiconductor device in the X-axis and Y-axis directions.
This trapezoidal speed command is a targeted locus for the head to be moved from a current position to a targeted position through the process of acceleration, constant velocity and deceleration. A typical method for generating a trapezoidal speed command involves determining the acceleration and the deceleration to be used, and changing the acceleration duration, the constant velocity duration and the deceleration duration in accordance with a targeted travel distance.
For example, when a travel distance xm, a maximum speed Vmaxm/s, and a maximum acceleration amaxm/s2 are given as a travel command as shown in FIG. 1, a targeted locus is generated for the travel distance by using the same acceleration until the speed reaches the maximum speed. The speed locus of this situation is triangular or trapezoidal, as shown in FIG. 2, and the acceleration duration and the deceleration duration vary in a triangular speed locus, that is, if a travel distance is between 0 and (Vmax2/amax)m.
In such a mounter, if the acceleration for moving the head is made faster for fast positioning, a greater reaction force is produced in moving the head, and vibration is more likely to occur from a base board of the mounter via a head supporting portion to the head.
To suppress the residual vibration in arriving at the targeted position within a targeted positioning precision, acceleration slower than the acceleration that a drive system of the head can intrinsically produce is used as the maximum acceleration.
When a targeted-value generating method having a fixed maximum speed and maximum acceleration as described above is used, however, the frequency properties of the acceleration and the deceleration components for the targeted locus varying with the acceleration and deceleration duration and the timing of starting the deceleration are not considered, although the conditions for the maximum speed and the maximum acceleration are satisfied.
Due to variations in the frequency properties of acceleration in this targeted locus, the condition of the residual vibration at the completion of positioning is changed at a control point for a subject of positioning, which is a problem.
To solve this problem, there is offered a method for reducing the residual vibration in the positioning control by controlling the acceleration duration and the deceleration duration.
To begin with, a first method (Japanese Patent Publication No. 60-29121, Japanese Patent Laid-Open No. 05-270786, Japanese Patent Laid-Open No. 06-170769, and Japanese Patent Laid-Open No. 07-328965) is a method for reducing residual vibration by setting the acceleration duration and the deceleration duration to be an integer multiple of a natural frequency of vibration. This method is employed in robot manipulators and cranes and is used for positioning in which the acceleration duration is an integer multiple of the residual vibration period.
However, in many cases, the mounter makes movements in which the acceleration duration is shorter than the vibration period of residual vibration. Therefore, when the acceleration/deceleration duration is lengthened to damp the residual vibration with a targeted locus by using this method as it is, it surely took a time equal to two periods of residual vibration in such a short distance that the targeted position is reached within the acceleration and deceleration duration, in the typical targeted locus (acceleration and deceleration duration, each 0.1 sec, equivalent to one period of residual vibration 10 Hz), as shown in FIG. 3, which has a problem in that the high speed is very difficult to achieve.
A second method (Japanese Patent Laid-Open No. 2000-298521) involves making the damping by the use of a database including the travel time and the degree of damping, while satisfying the conditions of the maximum speed and the maximum acceleration with the positioning time as a parameter.
However, with this method, it is required to create the data for the travel time and the degree of damping to effect the damping for each device, which has a problem in that the operation is very complex.
Moreover, a third method (Japanese Patent Laid-Open No. 05-108165) involves dividing by two a targeted locus obtained by adding a targeted locus and the same targeted locus shifted by a half period of a frequency set for damping (hereinafter referred to as a damping frequency) that is given at the time of making a travel command.
However, with this method, the damping can be performed on the vibration frequency that is an odd multiple of the damping frequency, but it cannot be made for an even multiple of the vibration frequency. Furthermore, the damping is possible for any two or more frequencies by repeating the same method in series twice or more, but there is a problem that the completion time of generation of the targeted locus is delayed by the time of adding a half period of the damping frequency.
Accordingly, as a condition for solving the problems of the first to third methods, it is desirable to change the acceleration duration and the deceleration duration in accordance with the vibration period of the residual vibration having the greatest amplitude that occurs at the positioning completion time to prevent this vibration from occurring as much as possible.
In view of the foregoing, an object of this invention is to provide a positioning device and method that can position a subject of positioning at a higher speed than conventional ones.
The foregoing object and other objects of the invention have been achieved by the provision of a positioning device for moving a subject of positioning to a desired position. The positioning device comprises a drive means for driving to move the subject of positioning and a control means for controlling the drive means to move the subject of positioning at a desired speed and acceleration based on a trapezoidal speed command. The control means controls the drive means to adjust the acceleration/deceleration duration of the subject of positioning and the timing of starting the deceleration to cancel the residual vibration in accordance with the vibration period of residual vibration that occurs immediately after positioning the subject of positioning.
As a result, this positioning device can efficiently cancel the residual vibration which occurs in the subject of positioning at the time of positioning.
Also, in this invention, a positioning method for moving a subject of positioning to a desired position moves the subject of positioning at a desired speed and acceleration based on a trapezoidal speed command and adjusts the acceleration/deceleration duration of the subject of positioning and the timing of starting the deceleration to cancel the residual vibration in accordance with the vibration period of residual vibration that occurs immediately after positioning the subject of positioning.
As a result, this positioning method makes it possible to efficiently cancel the residual vibration which occurs in the subject of positioning at the time of positioning.
As described above, in this invention, a positioning device for moving a subject of positioning to a desired position is provided with a drive means for driving to move the subject of positioning and a control means for controlling the drive means to move the subject of positioning at a desired speed and acceleration. The control means controls the drive means to adjust the acceleration/deceleration duration of the subject of positioning and the timing of starting the deceleration to cancel the residual vibration in accordance with the vibration period of the residual vibration that occurs immediately after positioning the subject of positioning. As a result, this positioning device can efficiently cancel the residual vibration which occurs in the subject of positioning at the time of positioning. Thus, it is possible to implement the positioning device that can position the subject of positioning at a higher speed than conventional ones.
Also, in this invention, a positioning method for moving a subject of positioning to a desired position moves the subject of positioning at a desired speed and acceleration and adjusts the acceleration/deceleration duration of the subject of positioning and the timing of starting the deceleration to cancel the residual vibration in accordance with the vibration period of the residual vibration that occurs immediately after positioning the subject of positioning. As a result, this positioning method makes it possible to efficiently cancel the residual vibration which occurs in the subject of positioning at the time of positioning. Thus, it is possible to implement the positioning method that can position the subject of positioning at a higher speed than conventional ones.
The nature, principle and utility of the invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings in which like parts are designated by like reference numerals or characters.